Periodontal disease is a disease that affects the oral cavity and its surrounding tissues as well as the teeth. Fusobacterium nucleatum is one of the Gram-negative bacteria involved in periodontal disease. With its proteins and receptors on the outer membrane, this species is known to invade oral epithelial cells and aggregate with early and late colonizers. Lemongrass plant extract (Cymbopogon citratus) has been shown to inhibit the growth of supragingival plaque bacteria in gingivitis patients. The objective of this research was to find out what the minimum inhibitory concentration (KHM) of lemongrass extract is on the growth of Fusobacterium nucleatum bacteria. The study involved the extraction of lemongrass extract as well as phytochemical tests on the extract. The Fusobacterium nucleatum bacteria were then grown at each concentration of lemongrass plant extract used in this study: 100%, 50%, 25%, 12.5%, 6.25%, 3.125%, 1.56%, and 0.78%. Furthermore, data analysis was performed on the obtained results. This study shows that lemongrass extract (Cymbopogon citratus) inhibits the growth of Fusobacterium nucleatum bacteria with a minimum inhibitory concentration (KHM) of 0.78% and a percentage of inhibition of 55.7%. This is due to the presence of many antibacterial ingredients in lemongrass plant extract, such as alkaloids, flavonoids, saponins, tannins, and phenols.